Nature vs. NurtureWe’re all born with a happiness baseline, so to speak. Research, some of it involving twins, indicates that at least 40 percent of happiness appears to be programmed into our genes and linked personality traits, dubbed our “set point” by psychologists. Our set point might be temporarily disrupted — say, by winning the lottery or the death of a loved one. Over time, though, we’ll likely revert back to our innate mood level.

But that theory is shifting, says Buettner, who aligns himself with researchers who believe that people can move along a personal spectrum, or “set range,” of happiness, at least within reason. “The guy born with a bad set of genes is probably never going to be a nine [on a 10-point scale], at least not for any sustained amount of time,” Buettner says.

As a whole, Americans are generally a happy group. About 85 percent of people report experiencing generally positive feelings — smiling, enjoyment, and happiness — every day, according to one of the most comprehensive windows into happiness, the Gallup-Healthways Well-Being Index. The analysis, published in 2010, relied on data from more than 450,000 responses to a daily survey conducted by the Gallup organization.

Income level certainly matters, but only to a certain point, according to the analysis. Its impact on daily mood levels off at roughly $75,000 annually, perhaps because that income covers daily needs and allows some latitude for leisure, including spending time with loved ones, the researchers theorize.

Another large-scale recent study, which sifted through 25 years of survey data from Germany, also highlights personal connections. Those individuals who consistently selected family or altruistic goals over money or possessions experienced higher levels of life satisfaction. Other factors fostered happiness: church attendance, participation in social events, and regular exercise.

Gretchen Rubin, as she focused on boosting her daily mood first for The Happiness Project blog and later for the related book, says one of her key breakthroughs involved reframing the prism through which she made even seemingly small decisions. Everyone consistently makes choices involving time, energy, or money, she says. “I would look at my life and say, ‘What is the impact [of this decision] on my relationships?’ That’s been a very good way to think about it.”